Black Rhinoceros
2007 Schools Wikipedia Selection. Related subjects: Mammals
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| Diceros bicornis Linnaeus, 1758 |
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Diceros bicornis michaeli |
The Black Rhinoceros, Diceros bicornis also colloquially Black Rhino is a mammal in the order Perissodactyla, native to the eastern and central areas of Africa including Kenya, Tanzania, Cameroon, South Africa, Namibia and Zimbabwe. Although the Rhino is referred to as a "Black" creature, it is actually more of a grey-white colour in appearance.
Like all species of rhinoceros, it is on the endangered species list due to excessive poaching for their horns, which are mostly used in dagger handles as a symbol of wealth in many countries, and as a febrifuge in Chinese traditional medicine. Contrary to popular opinion, only small amounts of the horns are consumed as an aphrodisiac. A poaching wave in the 1970's and 1980's wiped out over 96% of the Black Rhino populations across Africa.
The name of the species was chosen to distinguish it from the White Rhinoceros (Ceratotherium simum). This is very misleading, as those two species are not really distinguishable by colour. The word "White" in the name "White Rhinoceros" deriving from the Afrikaans word for "wide" rather than the colour white.
The World Conservation Union (IUCN) announced on 7 July 2006 that the West African Black Rhinoceros subspecies (Diceros bicornis longipes) has been tentatively declared as extinct.
Anatomy
An adult Black Rhinoceros stands 143 – 160 cm (56-63 inches) high at the shoulder and is 2.86-3.05 m (9.3-10 feet) in length. An adult weighs from 800 to 1400 kg (1,760 to 3,080 lb), exceptionally to 1820 kg (4,000 lb), with the females being smaller than the males. Two horns on the skull are made of keratin with the larger front horn typically 50 cm long, exceptionally up to 140 cm. Occasionally, a third smaller horn may develop. Skin color depends more on local soil conditions and their wallowing behavior than anything else, so many black rhinos are typically not truly black in colour.
The Black Rhinoceros is much smaller than the White Rhinoceros, and has a pointed, prehensile upper lip, which they use to grasp leaves and twigs when feeding. White Rhinoceros have square lips used for grazing grass. The Black Rhinoceros can also be recognized from the White Rhinoceros by its smaller skull and ears and its more pronounced forehead. Black Rhinoceros also do not have a distinguishing shoulder hump like the White Rhinoceros.
Reproduction
The adults are solitary in nature, coming together only for mating. Mating does not have a seasonal pattern but births tend to be towards the end of the rainy season in drier environments. The gestation period is 15 – 16 months; the single calf weighs about 35 – 50 kg at birth, and can follow its mother around after just three days. The mother and calf stay together for 2 – 3 years until the next calf is born; female calves may stay longer, forming small groups. The young are occasionally taken by hyenas and lions. Sexual maturity is reached from 5 years old for females, from 7 years for males, and the life expectancy in natural conditions (without poaching pressure) is from 35 – 50 years.
Ecology
The Black Rhinoceros has adapted to its habitat using the following characteristics:
- A thick, layered skin protects the rhino from thorns and sharp grasses.
- The soles of their feet are thickly padded to cushion the legs and absorb shock.
- The upper lip has been adapted for seizing and grasping (prehensile) objects which helps in browsing and foraging.
- The large ears rotate to give directional information on sound
- The large nose has an excellent sense of smell to detect predators.
- Two formidable horns are used for defense and intimidation.
- An aggressive disposition discourages predators. The animal's nearsightedness seems to urge the rhino to charge first and investigate later.
The Black Rhinoceros is a herbivorous browser that eats leafy plants, branches, shoots, thorny wood bushes and fruit. Their diet helps to reduce the amount of woody plants which results in more grasses growing for the benefit of other animals.
Their skin harbours many external parasites, which are eaten by oxpeckers and egrets that live with the rhino.
Subspecies
There are four subspecies of the black rhinoceros:
- South-central (Diceros bicornis minor) which are the most numerous, and once ranged from central Tanzania south through Zambia, Zimbabwe and Mozambique to northern and eastern South Africa.
- South-western (Diceros bicornis bicornis) which are better adapted to the arid and semi-arid savannas of Namibia, southern Angola, western Botswana and western South Africa.
- East African (Diceros bicornis michaeli) which had a historic distribution from south Sudan, Ethiopia, Somalia down through Kenya into north-central Tanzania. Today, its range is limited primarily to Tanzania.
- West African (Diceros bicornis longipes) is the rarest and most endangered subspecies. Historically, it once occurred across most of the west African savanna. Until recently, only a few individuals survived in northern Cameroon, but on July 8, 2006 the World Conservation Union declared the subspecies to be tentatively extinct.
Population
For most of the 20th century the continental black rhino was the most numerous of all rhino species. Around 1900 there were probably several hundred thousand living in Africa. During the latter half of the 20th century their number severely reduced from an estimated 70,000 in the late 1960s to only 10,000 to 15,000 in 1981. In the early 1990s the number dipped below 2500, and in 1995 it was reported that only 2,410 black rhinos remained. According to the International Rhino Foundation, the total African population has since then slightly recovered to 3,610 by 2003. According to a July 2006 report by the World Conservation Union, a recent survey of the West African Black Rhino, which once ranged across the savannahs of western Africa but had dropped to just 10, concluded the subspecies to be extinct. The northern white is soon to join the western black rhino on the extinction list as its last noted numbers were as few as 4. The only rhino that has recovered somewhat from the brink of extinction is the southern white whose numbers now are estimated around 14,500, up from only 50 a century ago.
